I have an old iMac G5 (without a webcam) that I would like to get running Ubuntu. The iMac has no hard drive in it, and I would like to get a live CD running so I can test out Ubuntu before I buy a hard drive to boot from, but I'm having trouble running the live CD.

When I put it in my iMac and held down the 'C' key to boot from a CD/DVD, the SuperDrive spins up, spins down, and ejects the disk. The iMac then displays a folder with a question mark superimposed on it (the icon for a missing startup disk).

I've read that this means the CD is not suitable to boot on that computer. According to the Ubuntu PowerPC FAQ (https://wiki.ubuntu.com/PowerPCFAQ), my iMac is compatible.

Are you copying the iso file to the DVD, or installing it? If you are not installing it properly, you will get this error, as the boot sector will take a look at it and think that it's just a file, not an OS.
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SimplySimonAug 12 '13 at 15:47